Many search engines provide content manipulation tools that modify a result set in order to merchandise particular items. Most basically, search engines present results ranked by their relevance to the user's query, determined by information-retrieval considerations and search algorithms. In addition, some search engines modify the ranking of the results based on additional considerations, such as business considerations. For example, in response to the query “bicycle,” a search engine may choose to promote a certain brand within the search results, and display some of the models of this brand among the top ten results.